Decarboxylative Giese additions through electron donor-acceptor complexes under transition metal-free conditions

Herein, we describe a transition metal-free Giese addition reaction method based on RAEs/HEH complexes under thermal conditions. Mechanistic experiments have shown that a well-known free radical decarboxylation process is necessary, which is achieved by slight heating of RAEs/HEH complexes. DFT calculations indicate that compared to individual RAEs, the RAEs/HEH complex is more conducive to the formation of the corresponding carboxyl radicals. The protocol could be carried out on a gram scale and was applied to deuterated alkyl carboxylic acid and dehydrocholic acid, indicating its utility for synthesizing the derivatives of carboxylic acid compounds. The excellent tolerance to water and oxygen makes this method highly suitable for late-stage modification of complex natural products.